No longer set EPOCDEVICE as it causes an error in createpackage.
Remove obsoleted code calling signis.exe and package file rewriting.

- Autodetect SDK by environment variable EPOCROOT and qt directory
below.
- Environment::appendOrSet/prependOrSet: Avoid duplicate entries
- Rename toolchain enumeration value
- Adapt S60ToolChainMixin to new GnuPoc setup, provide routines for
  all required variables.
- RVCTToolChain: Make RVCT detection smarter (Check for RVCT<v1><v2>BIN
  variable). Set all required variables in case of RVCTToolChain/GnuPoc
- QtVersionManager: Detect toolchain and Qt version properly, make S60
  device run config accept toolchain.
- Modify S60DeviceRunControl to execute 'make sis'
- Modify S60Devices::detectQt...() to check for Qt installed into SDK
  first and symlink as fallback.

QString: Use QChar/char where appropriate, do not use QString::null

Reviewed-by: dt

Display the error in a label of the preferences page.
Reviewed-by: con

 * Update list of system pathes.
 * Consistently use / as directory separator internally.

Reviewed-By: con

Factor out the initialization setting up the environment and headers in
the RVCT/GCCE toolchains.
Modify the RunControl to be able to support different package
building/signing processes.

Users can specify a S60 SDK root for Qt for Symbian versions
now.

Reviewed-by: con

- Introduce a communications device type flag, add stubs for
  Bluetooth to serialdevicelister and pass the device type
  in new struct CommunicationDevice along to run configuration
  and debugger start parameters (overriding the debugger settings).
- Give the s60devices::Device a tooltip in the settings page

At the moment you need to close and reopen the preferences dialog though.